LONG BEACH - Possible student cheating incidents at a dozen California schools, including Long Beach's Millikan High School, have delayed the release of the state standardized test results this year, officials said.

The California Department of Education is investigating 11 high schools and one middle school after students taking the Standardized Testing and Reporting exam, known as STAR, in April posted images of test materials on social networking sites, said Department of Education spokeswoman Pam Slater.

In the Long Beach Unified School District, a 10th- grader at Millikan apparently posted an image from a geometry test on a social networking website, said LBUSD spokesman Chris Eftychiou.

A Millikan administrator met with the student and a parent and the school is now determining what discipline will be taken, he said.

"In any case, we'll revisit this issue with test coordinators at the schools to keep testing conditions as secure as possible," Eftychiou wrote in an email. "About 18,000 high school students took these tests in our school district this year, and this was the only breach reported here, but we take it seriously. We're firmly committed to protecting the integrity and fairness of the testing process."

The STAR test results were originally expected to be released in mid-August but will now be released on Aug. 31, Slater said. The delay will push back the release of the state's Academic Performance Index scores, which are now expected in early October.

So far, experts haven't found evidence that the online images had a significant impact on test results, Slater said.

However, the Department of Education is still investigating and is expected to decide this week how it will handle incidents at each school, she said, adding that in a worst-case outcome, a school's test scores could be disqualified.

Other schools under investigation include:

Castillero Middle in San Jose

Glendale High

North Monterey County High

Rowland High in Rowland Heights

Oak Hills High, Hesperia

San Jose High

Mar Vista Senior High, Imperial Beach

Strathmore High in Porterville

University City High in San Diego

Watsonville High

North Hollywood High

Slater said a student who allegedly cheated claimed to attend North Hollywood High on a social media site but is possibly attending a charter school.